1. Field of the Invention
The present invention relates to a display device that can simultaneously display two images, and more particularly to a display device that can realize glasses-free 3D display or display two different images in each observation direction by using an optical deflecting member such as parallax barrier or a lenticular lens.
2. Description of the Background Art
In recent years, a glasses-free 3D image display that can display a 3D image without a need of special glasses has been proposed.
For example, Japanese Patent No. 2857429 describes a 3D image display device including barrier generating means that generates a parallax barrier stripe by an electric control of a transmissive display element, a display screen arranged posteriorly to the generation position of the parallax barrier stripe with a predetermined distance, and image display means that can output and display a multi-direction image in which a strip for a left image and a strip for a right image are alternately arranged corresponding to the parallax barrier stripe onto the display screen during the display of a 3D image.
In the 3D image display device described above, the barrier stripe is electrically generated, and the shape (the number, width, and space of stripes), position (phase), and density of such barrier stripe can be variable controlled freely. Therefore, this display device can be used as not only the 3D display device and its display method but also a 2D image display device and its display method, whereby this patent describes that a compatible image display device and image display method can be realized.
Japanese Patent No. 3668116 describes a 3D video image display device including image display means that alternately displays a stripe-like left-eye image and a stripe-like right-eye image, light-shielding means that is configured to be capable of moving a light-shielding unit, which generates a binocular parallax effect, with a pitch of ¼ of the pitch of the light-shielding unit, a sensor that detects a motion of a head of an observer in a horizontal direction and detects whether the position of the head of the observer is outside an effective zone in the front-back direction, and divided area movement control means. This patent describes that the divided area movement control means controls to allow the light-shielding unit of the light-shielding means to move or not to move for each divided area according to the state where the position of the observer's head is outside the effective zone in the front-back direction.
In the 3D image display device described in Japanese Patent No. 3668116, when the head of the observer moves to the shifted position, the movement of the light-shielding unit is controlled, and the display of the image display means is controlled, whereby a right-eye image can be fed to the right eye of the observer. Since a left-eye image can be fed to the left eye of the observer in this case, the observer can recognize a 3D video image.
Japanese PCT National Publication No. 2011-505017 describes a directional display device (3D image display device) including a display panel that includes a sub-pixel repetitive group containing eight sub-pixels including a first main-color sub-pixel, a second main-color sub-pixel, a third main-color sub-pixel, and a fourth main-color sub-pixel, and arranged in 4×2 matrix, the eight sub-pixels including the first main-color sub-pixel, the second main-color sub-pixel, the third main-color sub-pixel, and the fourth main-color sub-pixel in each row; a driving circuit that transmits a signal to each sub-pixel on the display panel; and an optical induction member that guides light emitted from a first group (sub-pixel group for right-eye image) of the sub-pixels on the display panel to a first visual field window (in the direction of a right eye), and guides light emitted from a second group (sub-pixel group for left-eye image) of the sub-pixels on the display panel to a second visual field window (in the direction of a left eye).
It is described that the 3D image display device in Japanese PCT National Publication No. 2011-505017 can provide an image having correct color information even as a single right-eye image and as a single left-eye image.
Japanese Patent No. 3096613 describes a 3D display device including a video image display panel in which right-eye pixels displaying a right-eye video image and left-eye pixels displaying a left-eye image are alternately arranged on all lines and all rows (checkered flag pattern); and an optical filter (parallax barrier or lens) that is arranged to the side close to an observer, of the video image display panel, has openings corresponding to the right-eye pixel and the left-eye pixel, and separates light from the right-eye pixel and light from the left-eye pixel to output the resultant to the observer.
According to the 3D display device described in Japanese Patent No. 3096613, the left eye and the right eye respectively observe a video image equivalent to a video image displayed onto a liquid crystal panel having a horizontal pixel pitch equal to the horizontal pixel pitch of the used liquid crystal panel. Accordingly, the number of the pixel rows in the horizontal direction is not decreased, so that the observer does not feel the presence of vertical stripes as in the conventional case.
However, in the 3D display device described in Japanese Patent No. 2857429 and Japanese Patent No. 3668116, the observer feels brightness variation during the electric control of moving the barrier light-shielding unit and the display control of the image display means according to the motion of the observer's head. The observer especially feels uncomfortable when the observer's head moves greatly, and the changeover is frequently made. There is a problem that the brightness variation is noticeable on the boundary where the parallax direction is changed.
In the glasses-free 3D display or in the two-image display that displays different images for each observation direction, using the optical polarizing member of a vertical stripe shape, such as a parallax barrier or lenticular lens, and a display panel, as described in Japanese Patent No. 2857429 and Japanese Patent No. 3668116, the resolution of the image in the horizontal direction viewed from one observation direction is reduced to ½. Similarly, in the 3D image display device described in Japanese PCT National Publication No. 2011-505017, the resolution of the image in the horizontal direction viewed from one observation direction is reduced to ½.
As a countermeasure, the structure described in Japanese Patent No. 3096613 is considered, the structure including a video image display panel in which right-eye pixels displaying a right-eye video image and left-eye pixels displaying a left-eye image are alternately arranged on all lines and all rows; and an optical filter (parallax barrier lens) that is arranged to the side close to an observer, of the video image display panel, has openings corresponding to the right-eye pixel and the left-eye pixel and separates light from the right-eye pixel and light from the left-eye pixel to output the resultant to the observer. However, according to this structure, the visible angular range in the vertical direction is narrowed, and the brightness efficiency is deteriorated, compared to the case where the optical filter (parallax barrier or lens) having vertical-stripe openings is used. This structure also needs not only the positioning in the horizontal direction and matching in angle but also the positioning in the vertical direction, when the optical filter and the video image display panel are assembled. This makes the assembling work difficult.